Engine load limiting controls



.Jam 13 1959 l L. J. MouLToN 2,868,184

ENGINE LOAD LIMITING coNTRoLs Filed April 22, 1957 l Huw/nf INVENTOR..ENG/NE I; FUEL mx/:ss L. J. M0 u1. To/v' 6 vra/1g Hf. V

ENGINE LOADLIMITING CONTROLS Lloyd Jackson Moulton, Mentor, Ohio,assignor to Curtiss-Wright Corporation, a corporation of DelawareApplication April z2, 1957, serial No. 654,401

s claims. (c1. 12s-140) This invention relates to an improved mechanismfor automatically compensating for changes in air supply pressure in theoperation of internal combustion engines, particularlyturbo-supercharged diesel engines.

The principal object is to provide` a simple and effectual arrangementacting through a hydraulic engine governor of known type to maintaineflicient combustion in the governed engine particularly by limiting thefuel being supplied to the engine in accordance with variations inengine air supply pressure as well as in accordance with engine speedand other conditions which affect operation of governed engines. t

lt is well known that a supercharged diesel engine and particularlyturbo-supercharged diesels cannot operate efficiently at high powerlevel unless its air pressure is properly mated to the rate of fuelsupply, and that when engine speed is caused to change by suddenapplication of load, or when the speed setting of the governor of the`tion of the herewith diagrammatically illustrated embodiment.

The accompanying drawing is a schematic view showing a typical fluidcircuit of a hydraulic governor whose casing preferably contains orsupports the principal elements required for practice of the presentinvention.

The hydraulic governonas shown, has a casing A, containing anengine-speed-change-detector or speed weighing mechanism B withliyweights B', a Speeder spring C, settable for engine speed as bymember S', and a pilot valve D the movable part of which is valveplunger P. The pilot valve D controls the operating eifect ofsubstantially constant pressure fluid (governor oil as from a `pump andaccumulator, not shown, admitted to passage F) on a servomotor,represented by power piston H and itscylinder. Passage F is continuouslyconnected to the cylinder space or pressure chamber l of the servomotor,

` and passage G connects the pilot Valve D with the cyliner chamber l.Governor oil, in the illustrated equilibrium or neutral position of thepilot valve, is trapped by that valve in line G in contact with arelatively larger eifective area of the power piston H whose smallerelfective area is continually subjected to governor oil prest sure inchamber I.

To cause increased-fuel movements of the power piston H (upward asshown) the pilot Valve plunger (by lowering as in response to diminishedengine speed, thus opening port E) admits governor oil through passage Gto the cylinder chamber J of the power piston; and to cause de- StatesPatent Patented Jan. 13, 1959 creased-fuel power piston movements thepilot valve plunger P is moved to spill trapped oil from said chamber Iat one of the various sump-connected ports, all indicated S..

A hydraulically acting temporary speed droop or` compensation systembetween the governor power piston H and its pilot valve D isdiagrammatically represented by an actuating displacement pump Noperatedby power piston H; oil passage O; receiving piston Q which isspring-connected to the pilot valve plunger P, and a needle valve R forreset rate adjustment in a well known manner.

A load limiting valve of known type is represented generally at L, themovable portion of the valve being a valve plunger M. Downward movementof valve plunger M from its illustrated neutral position first blockspassage G leading from the pilot valve D to the power piston cylinderchamber l, and then connects the chamber I to sump. Thereby themechanism L functions to circumvent operation of the governor pilotvalve D to cause fuel-increasing movement of the power piston H such asnormally occurs, or would occur, with increase in engine load. Thegovernor pilot valve D dominates fuel-decreasing movement of the powerpiston H at all times through operation to spill governor o-il fromchamber J via a one way operating by pass valve L connected essentiallyas shown.

Load limiting can, alternatively, be accomplished through operation ofthe pilot valve D, conditionally as a function of power piston movement,as is well known (not illustrated); and the present invention can beused with that type of load limiting valve mechanism without substantialmodification (e, g. by reversal of output direction of the presentlinkage or by provision of hydraulic linkage to move pilot valve plungerP upwardly to limit load).

In the load limiting valve mechanism L, as schematically shown, upwardor increased-fuel movement of the power piston H beyond a predeterminedreadily adjustable effective position, as will be described, operatesconditionally as through a tailrod H of the piston upon a lever lt),having a normally fixed pivot '11, to depress the valve plunger M andstop further fuel-increasing movement of the power piston. Lever 1li)operates the valve plunger M through the intermediary of a floatinglever 2li pivotally connected as at 21 to said valve plunger, theoperating connection between the two levers being illustrated as a pushrod Z2 in a suitable guide.

In order that the load limiting valve M can be operated irom itsillustrated neutral position downwardly to an appropriate fixed stop,the tailrod H has a one-wayyieldable connection with the power piston H.This, as shown, includes a threaded stop collar 24 in a sump-exposedtrunk portion of the power piston, and a head portion 25 on the tailrodwhich is held in upward abutment with the collar 24 by a spring 26 inthe piston H below the head portion of the tailrod. Spring 2o has, ofcourse, more eiective force than the return spring M of the valveplunger M. Pivot lll for lever lt) is adjustable vertically, to changethe point in upward power-piston-stroke at which the load limitingoperation can be made to occur. As shown, a supporting bracket 12 forpivot li is arranged to be raised and lowered by adjustment of a screw13 swivelled to bracket 12 and inthreaded engagement with a relativelyfixed bridge portion T of the governor casing A. A tubular lock nut 14for the screw 13 and the screw itself via the interior of the nut, arereadily accessible for manipulation in an upper portion of the governorcasing. A rod 15, slidably guided by casing portion T, cooperates withthe adjusting screw 13 to hold the fulcrum-supporting bracket 12 inposition horizontally. The guide rod 15, as shown, is connected tooperate a load indication device 16 in reference to a suitable dial 17externally of the governor casing, so that the power piston position atwhich,

es load limiting under predetermined conditions occurs can be madeapparent to an operator.

For operation of the load limiting valve plunger M in response to actualengine speed and/or in response to engine charging air pressure (or anassociated forceproducing function) a floating lever Ztl is pivotallyattached to the valve plunger M as at 2l, and the pushrod or actuating pin 22 is located for fulcrum-establishing contact with the lever Ztl sothat predetermined fuelincreasing movements of the power piston H arecommunicated provisionally to the floating lever 29, e. g. in accordancewith existing engine speed and/or in accordance with -existing enginecharging air pressure, each independently of the other and by positiveaction on the valve M.

Engine-speed-rneasuring or tachorneter mechanism K, as shown, comprisesa Well known combination including flyballs K1 and a spring K2(partially shown) acting oppositely of the flyballs. The spring K2 as afunction of decrements of engine operating speed moves the lever 20about its fulcrum 22, through the intermediary of a push rod K3,tochange the operating relationship between the governor power piston Hand the load limiting valve L (such as primarily established byadjustment of fulcrum ll). Thereby, at a sufficiently low speed (subjectto adjustment by means not shown) such that increase of fuel can bedetrimental to the engine, the fuel cannot be increased beyond apredetermined point. Similar mechanisms in governors are commonly calledbrake mean effective pressure (B. M. E. P.) limiters, and their mannerof operation is well known in the governor art.

The engine-charging-air-pressure-resporisivc mechanism W hereof, asschematically illustrated in part, comprises a diaphragm or bellowsdevice 31 of suitable design mounted in or on the governor casing A andhaving a signal receiving conduit connection 32 with (e. g.) the enginecharging air box, and an output element 34, shown as a rod attached to amovable wall of the bellows device and operatingly connected to the loadlimiter floating lever 2i) as will be describe-d.

As engine air pressure, or its operative equivalent in terms ofsupplying a combustion-supporting medium under pressure to the engine,is reduced or becomes depleted-the output rod 34 of mechanism W is movedby a reactance or operating spring 35, shown as acting on the rod 34, tooppose the pressure-produced motion of the rod, and movements of the rodare communicated to the tioating lever Ztl as through a bell crank 36and link 3%5 as clearly shown. The link 38 has an abutment portion 39underhanging the same effective portion of the oating lever Ztl as isacted upon by the engine speed measuring mechanism K. The arrangement issuch that the two mechanisms K and W are mutually independent, bothacting upon the lever 2Q in the same direction but without possibilityfor the action of either mechanism interfering with the action of theother in complementing governor power piston action to limit increase ofengine fuel.

In order to minimize sliding friction the vario-us points or regions ofinput action on the floating lever Ztl (and similar points on the leverill) are preferably along a common longitudinal axis (such `as indicatedat 20a in respect to the floating lever 20 for example). Axis 20aintersects the axis of pivotal connection 2l or the output point of thefloating lever 20 in reference to load limiting valve plunger M.

ln order to mate the operation of present mechanism W to an engine it isnecessary to be able to oppose the force being exerted on the outputelement 34 of enginecharging-pressure-responsive mechanism W with aloadlimiting-valve-operating force proportional to the eliectivecharging air pressure force or whatever pressure signal is used. Anappropriate operating-force-adjustment is shown in the form of a screw35 serving as a normally stationary reactance element for spring 3S. Thespring 35 is in such position in the governor that it can be readilyreplaced by a spring of a different scale when that is necessary inorder to meet specific engine requirements, e. g., in order to adapt themechanism fo-r service on different types or makes of engines. Stroke ofthe mechanism W, as applied to the lloating lever 20, can be adjusted bymoving the upper end of the link 38 along the lower arm 36 of the bellcrank lever 36 by shiftable pivot device 37 including suitable lockingmeans not shown. Additionally the brackets 31a, 35a and 36a which, asshown, support theprincipal operating elements of the mechanism W can beshifted horizontally into different positions on the superstructure ofthe governor casing.

All the necessary adjustments pointed out -above can be accomplished oreffected externally of the principal governor casing; i. e., at itsupwardly exposed or top side, after removal of a suitable casing cap orcover (not shown).

Emergency. shutdown devices, such as represented by rod 4t) and solenoid41, can be arranged to act directly upon the load limiting Valve plungerM without interfering with the hereinbefore described load limitingoperations. A hand shut-down device such as 44 is shown as arranged tooperate more or less independently of the other load control andshut-down mechanisms (e. g., via the rod 4u).

l claim:

l. An internal combustion engine control mechanism, including ahydraulic governor of the servomechanism type, wherein speed responsivemeans in the governor operates through a governor pilot valve to changethe position of a governor output motor element whereby to increase anddecrease fuel to the engine, and wherein means associated with theengine operates to supply air under variable pressure capable ofsupporting combustion; the combination of a load limiting valvemechanism in the governor operative to prevent normal speed responsiveaction of the pilot valve from increasing engine fuel via the outputmotor element, means capable of actuating said load limiting valvemechanism primarily and conditionally as a function of movements of saidoutput motor element in `its fuel-increasing direction to limit suchmovements, and pressure responsive means in the governor connected foroperation as a function of the air supply pressure producing means andoperating on said load limiting valve mechanism to change the operatingrelationship between the output motor ele ment and said valve mechanism.

2. The engine control mechanism according to claim l wherein a maincasing houses the governor elements mentioned, the air pressureresponsive means includes a diaphragm or bellows device in fixedposition on the casing and having an output member connected to operatethe load limiting valve mechanism, a spring connected to oppose pressureoperated motion of the output member of said device, and readilylaccessible adjusting means operable on the spring to vary its force.

3. An internal combustion engine control mechanism, including ahydraulic governor of the servomechanism type, wherein speed responsivemeans in the governor operates through a governor pilot valve to changethe position of a governor output motor element whereby to increase anddecrease fuel to the engine, and wherein means associated with theengine operates to supply air under variable pressure capable ofsupporting combustion; the combination of a load limiting valvemechanism in the governor operative to prevent normal speed responsiveaction of the pilot valve from increasing engine fuel via the outputmotor element, a lever capable of actuating said load limiting valvemechanism primarily as a function of movements of said output motorelement in its fuel-increasing direction to limit such movements, afirst means operating on a portion ofthe lever in one direction ofoperation of the lever to change the operating relationship between theoutput motor element and the load. limiting valve mechanism, and asecond means operated variably as a function of the air supply pressureproducing means and operating on said lever to change said relationship,said first and second means operating on an effectively common portionof the lever in a single direction but without being capable ofoperating thereon in an opposite direction, whereby the operations ofneither of said two means can affect the operation of the other.

4. An internal combustion engine control mechanism, including ahydraulic governor of the servomechanism type, wherein speed responsivemeans in the governor operates through a governor pilot valve to changethe position of a governor output motor element connected to increaseand decrease fuel to the engine, and wherein means associated with theengine operates to supply air under variable pressure capable ofsupporting combustion; the combination of a load limting valve in thegovernor between its pilot valve and its output motor element so as tobe operative to prevent pilot valve action from increasing fuel via theoutput motor element, a lever capable of actuating said load limitingvalve primarily as a function of movements of said output motor elementin its fuel-increasing direction to limit such movements, engine speedresponsive means operating on a portion of the lever in one direction ofoperation of the lever to change the operating relationship between theoutput motor element and the load limiting valve so as to limit increaseof fuel to the engine as a function of decrements of operating speed ofthe engine, and an additional means operated variably as a function ofthe air supply pressure producing means to change said relationship,said engine speed responsive means and additional means operating on aneffectively common portion of the lever in a single direction butwithout being capable of operating thereon in an opposite direction,whereby the operations of neither of the two means can affect theoperation of the other.

5. An internal combustion engine load control, mechanism, including ahydraulic governor of the servomechanism type, wherein speed responsivemeans in the governor operates through a governor pilot valve to changethe position of a governor output motor element connected to increaseand decrease fuel to the engine, and wherein means associated with theengine operates to supply air under variable pressure capable ofsupporting combustion; the combination of a load limiting valve plungerin a motor element fluid supply passage of the governor between itspilot valve and its output motor element so as to be operative toprevent pilot valve action from increasing fuel via the output motorelement, a floating lever pivotally connected to the plunger of the loadlimiting valve, abutment means connected for operation on a portion ofthe lever as a function of movements of said output motor element in itsfuel-increasing direction thereby provisionally to cause load limitingmovement of the valve plunger, engine speed responsive means in thegovernor operating on another portion of the floating lever in adirection to change the operating relationship between the output motorelement and the floating lever, and pressure operated means connectedfor operation variably as a function of the air supply pressureproducing means to change said relationship, said engine speedresponsive means and said pressure operated means operating on .aneffectively common portion of the floating lever in a single direction,whereby the operations of neither of the two means tends to affect theoperation of the other.

6. The mechanism according to claim 5, wherein the load limiting valveplunger and the governor output motor element are guided for movement inmutually parallel paths, motion of said motor element is provisionallyimparted to the valve plunger via a lever having a normally Xed fulcrum,a supporting member for the fulcrum, and means connected to thesupporting member and movable for adjustment in a direction parallel tothe movement of the motor element and valve plunger so as to change theprovisionally operating relationship between the motor element and thefloating lever.

7. The mech-anism according to claim 6, wherein a device `connected tothe lever fulcrum supporting member is moved thereby when the supportingmember is adjusted in position, and means on the governor externallythereof connected for and capable of indicating to an operator variouspositions of said device as moved by the fnlcrum supporting member.

8. The mechanism according to claim 5, wherein the abutment meansoperated as a function of governor output motor element movement, theengine speed responsive means and the pressure operated means act uponthe floating lever in a common plane along a longitudinal axis of thefloating lever.

References Cited in the file of this patent UNITED STATES PATENTS2,690,167 Moulton Sept. 28, 1954

